We have generated continuously prpagatable T cell clones to study the biochemical basis of specific T cell functions. All Ly2+ clones mediate suppressor activity and all Lyl+2- clones mediate helper activity; each type (helper or suppressor) secretes a characteristic pattern of polypeptides. We have purified one antigen-specific suppressor protein (70,000 daltons) from a glycophorin-specific Ly2+ T-cell clone. We have also purified a 45,000 dalton protein from h supernatant of Lyl clones and this 45K protein activated B-cells to secrete immunoglobulins. The aims of this project are: (1) purification of large amounts of 70K proteins from h supernatant of SRBC-specific and TNP-specific Ly2+ clones in order to study their structural and functional properties, with particular emphasis on the structure of constant (45K) and variable (24K) domains of the 70K protein (peptide mappig and sequencing); (2) modulation of the synthesis of proteins by Lyl TH clones exposed to the 70K suppressive protein; (3) generation of serological reagents that bind to the 70K Ts molecule; (4) generation of cDNA probes from mRNA coding for 70K proteins after translation of mRNA from Ly23 cloned cells, to study the genetic basis of T cell recognition of the antigen.